The tweet was posted just before 11am with a link to an article which said Mr Varadkar was closing in on victory.

However, it was deleted some time later by Mr Williams, with RTÉ insisting he made the decision himself.

RTÉ managing director of news Jon Williams

RTÉ is legally obliged to be impartial and has its own strict social media rules for staff.

These guidelines say the core guiding principle is "fairness and impartiality" and tell staff to avoid any activity that could be seen to be partisan.

Responding to Mr Williams's comment, Mr Coveney's campaign manager Damien English told the Irish Independent: "I would not expect the national broadcaster to either pre-judge the outcome of the election or make a comment on either candidate during the Fine Gael leadership contest.

"I would hate to see any bias brought into the reporting of the contest before any votes are cast. This election will be decided by the entire membership of the Fine Gael Party, no one else."

A spokeswoman for RTÉ said the decision to delete the tweet was made entirely by Mr Wiliams himself.

She said he had retweeted a link to an article and said he often did this.

He was just summing up the content of the piece in his post, she said. Having read it again after posting it, he decided to delete it.

"He didn't want people to think he was giving a personal opinion," the spokeswoman told the Irish Independent.

"He would regularly tweet articles from a number of different publications. He was summing up parts which were in the article.

"But he thought that could be misconstrued as giving his own opinion."

She said the word "coronation" also appeared in the original piece that Mr Williams had linked to.

When asked if someone in the organisation had asked or suggested to Mr Williams that he take down the post, the spokeswoman said the decision was made by him.

Mr Williams declined to comment when contacted by the Irish Independent yesterday.

He referred a request for comment to the press office.

In November last year, the national broadcaster announced the appointment of Mr Williams to his position as head of news.

From Liverpool, he had previously worked as managing editor for international news at ABC News in New York from March 2013.